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➡️ Introduction
Understanding task dependencies is essential for creating an accurate and realistic project schedule.
Dependencies determine how tasks are linked — which ones must finish before others can start, or which can run in parallel.
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Among the four main dependency types, Finish-to-Start (FS) and Start-to-Start (SS) are the most commonly used in project management.
This guide explains these two dependency types, their differences, and when to use each — with a visual, mobile-friendly table you can integrate directly into your site.
✅ What Are Task Dependencies?
A dependency defines the relationship between two activities in a project schedule.
It determines the order in which tasks are executed and how the delay in one can affect others.
Without defining dependencies clearly, your project schedule will be inaccurate, and you risk resource conflicts or timeline gaps.
✅ Finish-to-Start vs Start-to-Start Dependencies
Key differences, examples, and when to apply each dependency type in scheduling.
| Dependency Type | Definition | Example | When to Use |
|---|---|---|---|
| Finish-to-Start (FS) | Task B cannot start until Task A finishes. The most common dependency type in project scheduling. | You must finish writing a report (Task A) before you can review it (Task B). | Use when one task logically depends on the full completion of another. |
| Start-to-Start (SS) | Task B can start as soon as Task A starts, but both may continue in parallel. | Testing (Task B) can begin as soon as development (Task A) starts, progressing together. | Use to overlap tasks and shorten project duration when parallel work is possible. |
✅ When to Use Finish-to-Start
✔️ Most common dependency type (used in over 70% of project schedules).
✔️ Ideal when tasks have sequential relationships — one must be fully completed before the next begins.
✔️ Helps maintain clarity and control in complex, linear workflows.
Example Scenarios:
- Construction: “Lay foundation” must finish before “Build walls.”
- Software development: “Design UI” must finish before “Code interface.”
✅ When to Use Start-to-Start
✔️ Useful for overlapping activities to save time and accelerate delivery.
✔️ Effective in Agile and fast-paced environments.
✔️ Requires strong coordination to manage simultaneous work.
Example Scenarios:
- Marketing: “Write campaign content” and “Design visuals” start together.
- Engineering: “Test components” can start while “Assemble prototype” continues.
✅ Combining Both for Efficiency
In complex projects, project managers often use a mix of FS and SS dependencies.
For example:
- A Finish-to-Start link ensures logical sequencing.
- A Start-to-Start link introduces controlled overlap, improving efficiency.
Balancing these dependency types enables both structure and flexibility, optimizing project timelines.
✅ Common Mistakes to Avoid
❌ Overlapping tasks without resource planning.
❌ Using Start-to-Start on highly dependent or risky activities.
❌ Ignoring lag time between related tasks.
❌ Failing to update dependencies after schedule changes.
✅ Final Thoughts
Understanding Finish-to-Start and Start-to-Start dependencies empowers project managers to build more accurate, flexible, and efficient schedules.
Used wisely, these dependency types help prevent delays, reduce idle time, and ensure that each part of the project flows smoothly.
A great schedule doesn’t just list tasks — it defines how they move together.
